See here
http://office.microsoft.com/en-us/ex...993911033.aspx for Microsoft article on how to 'customise how Excel starts'
In particular - the bit about 'Save workbook settings you want to use every time you start Excel with a workbook template (book.xlt)'.
There is also another Microsoft article here ...
http://office.microsoft.com/en-us/ex...548151033.aspx
for 'customising Excel defaults with templates.
Another thing to try is to possibly open your spreadsheet - make the toolbar changes, then save the document as another name...its a long shot but might work.
I had an issue with a client yesterday where Word wasn't keeping settings...it turned out the Normal.dot was corrupt...in this case - the client wasn't concerned about recovering any previously 'saved' settings so I deleted the normal.dot and the temp version of the normal.dot in the same folder (found by doing a Windows search and searching hidden files/folders). Word now seems to be keeping settings...
I figured Excel has the same type of thing (hence the MS articles above) - if anything in those articles fails you - try finding the xlt's mentioned and possibly even the .xlb's and renaming them...this may restore original default settings and allow saving of new ones.
If you do - be sure to locate the temp versions (by searching the hidden files folders option in Windows search).
Hope this helps...